In sections II and III, Marlow often recounts sights he viewed through binoculars. Does using this technique provide Conrad with any benefits in telling story?

Certainly the sights that Marlow sees through his binoculars are new and often shocking to Marlow. This allows Conrad the freedom to expose the reader to exactly what Marlow is seeing and feeling. Marlow becomes the eyes or surrogate for te reader to experience the strange dark world.